Innervation of the mouse cornea stroma. Whole-mount staining of (A) E14.5 and (C) E15.5 and (E) E16.5 corneas showing progressive extension and branching of nerves as they innervate the entire cornea stroma. (D) Cornea in (C) imaged from an angle to show that a single major nerve bundle (arrow) from the posterior region of the eye bifurcates into several nerves (asterisks) in the VN quadrant. Cross-sections of (B) E14.5 showing that nerve bundles innervate only the anterior two-thirds of the stroma and project toward the epithelium, which is innervated by (F) E16.5 (arrowheads). Dotted lines demarcate in (E) the boundary of the area covered by nerves from each quadrant, and in (B) and (F) the epithelium/stroma boundary. DN, dorsal-nasal; VN, ventral-nasal; VT, ventral-temporal; DT, dorsal-temporal; oc, optic cup; st, stroma; epi, epithelium; ll, lower eyelid nerves. Scale bars: (A, C, D, E) 100 μm; (B, F) 50 μm.